linux-kernel - Re: [PATCH -v2 13/18] sched/fair: Propagate an effective runnable_load

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Message-ID: <64f045cc-31f3-4194-c3ea-6ea11f52b798@arm.com>
Date:   Tue, 3 Oct 2017 10:29:26 +0100
From:   Dietmar Eggemann <dietmar.eggemann@....com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     mingo@...nel.org, linux-kernel@...r.kernel.org, tj@...nel.org,
        josef@...icpanda.com, torvalds@...ux-foundation.org,
        vincent.guittot@...aro.org, efault@....de, pjt@...gle.com,
        clm@...com, morten.rasmussen@....com, bsegall@...gle.com,
        yuyang.du@...el.com
Subject: Re: [PATCH -v2 13/18] sched/fair: Propagate an effective
 runnable_load_avg

On 03/10/17 09:50, Peter Zijlstra wrote:
> On Mon, Oct 02, 2017 at 06:46:32PM +0100, Dietmar Eggemann wrote:
> 
>>> +/*
>>> + * Recomputes the group entity based on the current state of its group
>>> + * runqueue.
>>> + */
>>> +static void update_cfs_group(struct sched_entity *se)
>>
>> update_cfs_share(s)() is still mentioned in the function header of
>> update_tg_load_avg() and update_cfs_rq_load_avg().
>>
>> Should we rename those comments with this patch?
>>
>> IMHO, the comment for update_tg_load_avg() is still true whereas the one
>> for update_cfs_rq_load_avg() mentions cfs_rq->avg as
>> cfs_rq->avg.load_avg (or cfs_rq_load_avg()) and update_cfs_group()
>> doesn't use it anymore. It's now used in calc_group_runnable() and
>> calc_group_shares() instead.
>>
>> [...]
> 
> Right, so something like the below? Thinking that update_cfs_group()
> immediately leads to calc_group_*() so no need to spell those out.

Looks good to me, agreed.

> 
> 
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 350dbec01523..fee2e34812da 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -3333,7 +3333,7 @@ __update_load_avg_cfs_rq(u64 now, int cpu, struct cfs_rq *cfs_rq)
>   * differential update where we store the last value we propagated. This in
>   * turn allows skipping updates if the differential is 'small'.
>   *
> - * Updating tg's load_avg is necessary before update_cfs_share().
> + * Updating tg's load_avg is necessary before update_cfs_group().
>   */
>  static inline void update_tg_load_avg(struct cfs_rq *cfs_rq, int force)
>  {
> @@ -3601,7 +3601,7 @@ static inline void add_tg_cfs_propagate(struct cfs_rq *cfs_rq, long runnable_sum
>   * avg. The immediate corollary is that all (fair) tasks must be attached, see
>   * post_init_entity_util_avg().
>   *
> - * cfs_rq->avg is used for task_h_load() and update_cfs_share() for example.
> + * cfs_rq->avg is used for task_h_load() and update_cfs_group() for example.
>   *
>   * Returns true if the load decayed or we removed load.
>   *
>